The present invention relates to methods and apparatus for recognizing handwritten Chinese characters, and in particular to methods and apparatus for recognizing handwritten Chinese characters based on combinations of phonetic letter and stroke recognition.
Nowadays there exist various keyboard-based methods for inputting Chinese characters and various methods for recognizing handwritten Chinese characters. Among them the keyboard-based inputting methods (such as five-stroke method) generally need better training of the users so that the users can remember the character codes defined by means of phones, shapes and meanings of the characters for mapping them to the keyboard, so the methods cannot be easily used. The processes of recognizing handwritten Chinese characters usually comprise feature extraction, stroke recognition, sorting and other time-consuming and memory-consuming tasks. These handwritten recognition processes are able to recognize a Chinese character only after the user has finished writing all the strokes, and demand more system resources. Though these handwriting inputting methods can be employed on PC""s, it is not so easy to use these methods on computers having limited amount of resources, such as palm computers, electronic-notebooks, and personal digital assistants, because in such kinds of computers the CPU speed is rather low and the memory size is extremely limited. Furthermore, the recognition rate of handwritten Chinese characters is rather low, demanding much time in correcting the errors.
The first object of the present invention is to provide a method for recognizing handwritten Chinese characters based on stroke recognition.
The second object of the present invention is to provide a method for recognizing handwritten Chinese characters based on combination of stroke recognition and phonetic letter recognition.
The third object of the present invention is to provide an apparatus for recognizing handwritten Chinese characters based on stroke recognition.
The fourth object of the present invention is to provide an apparatus for recognizing handwritten Chinese characters based on combination of stroke recognition and phonetic letter recognition.
To accomplish the first object, the present invention provides a method for recognizing handwritten Chinese characters, characterized by comprising the following steps: a step of recognizing strokes, detecting the movement of a pen between pressing down and lifting up of the pen when a user uses the pen to write in strokes a Chinese character/phrase, identifying the pen movement with at least one stroke code, and forming at least one new stroke code sequence respectively with each one of the at least one stroke code and previously formed stroke code sequences; a step of retrieving in dictionaries/lexicons stored in a computer memory at least one dictionary/lexicon entry which corresponds to the at least one new stroke code sequence formed in the step of recognizing strokes, so as to obtain at least one candidate Chinese character/phrase; a step of dynamically displaying the at least one candidate Chinese character/phrase at the same time when the user writes the strokes; a step of jumping to the above-mentioned step of recognizing strokes when it is judged that the user goes on writing the next stroke; a step of generating recognition results, in which if it is judged that the user has selected one of the at least one candidate character/phrase, regarding the selected Chinese character/phrase as a recognition result of the handwritten Chinese characters/phrases.
To accomplish the second object, the invention provides a method for recognizing handwritten Chinese characters, characterized by comprising the following steps: a step of recognizing phonetic tags, detecting the handwritten phonetic tags of the Chinese character/phrase and determining a range of entries in the dictionaries/lexicons based on the phonetic tag; a step of recognizing strokes, detecting the pen movement between pressing down and lifting up of the pen when the user uses the pen to write in strokes a Chinese character/phrase, identifying the pen movement with at least one stroke code, and forming at least one new stroke code sequence respectively with each one of the at least one stroke code and previously formed stroke code sequences; a step of retrieving in the range determined in the above step of recognizing phonetic tags at least one character/phrase entry which corresponds to the at least one new stroke code sequence formed in the step of recognizing strokes, so as to obtain at least one candidate Chinese character/phrase; a step of dynamically displaying the at least one candidate Chinese character/phrase; a step of jumping to the above-mentioned step of recognizing strokes when it is judged that the user goes on writing the next stroke; a step of generating a recognition result, in which if it is judged that the user has selected one of the at least one candidate character/phrase, regarding the selected Chinese character/phrase as a result of recognition of the handwritten Chinese characters/phrases.
To accomplish the third object, the present invention provides an apparatus for recognizing handwritten Chinese characters, characterized by comprising: means for recognizing strokes, detecting a pen movement between pressing down and lifting up of the pen when a user uses the pen to write in strokes a Chinese character/phrase, identifying the pen movement with at least one stroke code, and forming at least one new stroke code sequence respectively with each one of the at least one stroke code and previously formed stroke code sequence; means for retrieving in dictionaries/lexicons stored in a computer memory at least one character/phrase entry which corresponds to the at least one new stroke code sequence, so as to obtain at least one candidate Chinese character/phrase; means for dynamically displaying the at least one candidate Chinese character/phrase; means for generating a recognition result, based on the displayed at least one candidate character/phrase selected by the user, regarding the selected Chinese character/phrase as a result of recognition of the handwritten Chinese characters/phrases.
To accomplish the fourth object, the present invention provides an apparatus for recognizing handwritten Chinese characters, characterized by comprising: means for recognizing phonetic tags, detecting the handwritten phonetic tags of the Chinese character/phrase and determining a range of entries in the dictionaries/lexicons stored in a computer memory based on the phonetic tags; means for recognizing strokes, detecting a pen movement between pressing down and lifting up of the pen when a user uses the pen to write in strokes a Chinese character/phrase, identifying the pen movement with at least one stroke code, and forming at least one new stroke code sequence respectively with each one of the at least one stroke code and previously formed stroke code sequence; means for retrieving in the range determined by the means for recognizing phonetic tags at least one character/phrase entry which corresponds to the at least one new stroke code sequence, so to obtain at least one candidate Chinese character/phrase; means for dynamically displaying the at least one candidate Chinese character/phrase; means for generating a recognition result, based on the displayed at least one candidate character/phrase selected by the user, regarding the selected Chinese character/phrase as a result of recognition of the handwritten Chinese character/phrases.
The methods of the invention make use of the feature of handwriting of the Chinese characters, i.e. stroke by stroke. The recognition rate of such recognizing methods are limited in two aspects: the rate of stroke recognition and the number of strokes in handwriting of a character.
As the object set to be recognized in the invention includes only strokes of Chinese characters (about several tens of strokes), which are much less than the total number of Chinese characters, it is possible to specially design methods for recognizing strokes by using limited amount of resources, so that there will be much higher probability that correct results of stroke recognition will be among the candidate strokes, thereby having relatively high stroke recognition rate (e.g. by using the features of direction of pen movement and change of the direction with time to recognize the strokes). At the same time, man-machine interactive inputting method allows the users to easily correct the recognizing errors of the just input strokes. Besides, the methods of the invention display the candidate Chinese characters/phrases on-line, so the users are able to input the handwritten Chinese character without the need of finishing writing all the strokes of the Chinese character. The methods of the invention take account of these two factors of higher recognizing rate of strokes and smaller number of strokes, thereby having higher recognition rate.
The second method of the invention makes use of the popular Chinese character Pinyin system to make the range of retrieving stroke code sequences smaller. Firstly, as the number of Pinyin alphabets is rather limited, rather high recognizing rate can be attained by using specified methods but using only limited amount of resources. Meanwhile, as the number of Chinese characters having the same first Pinyin alphabet is small, far less than the total amount of Chinese characters (it has been estimated that the maximum number of Chinese characters having the same first Pinyin alphabet is no more than 400), the retrieving range can be greatly reduced so as to remarkably raise the recognition rate of the methods of the invention. The number of strokes handwritten by the users is small, so the speed of inputting is higher and the methods can be easily employed.
The methods of the invention can be easily used to input handwritten Chinese characters to the computers with limited resources, such as palm computers, electronic notebooks and personal digital assistants.